API 호출 후 취소하기

https://medium.com/little-big-programming/%EB%82%B4%EA%B0%80-fetch-api%EB%A5%BC-%EC%93%B0%EC%A7%80-%EB%AA%BB%ED%96%88%EB%8D%98-%EC%9D%B4%EC%9C%A0-3c23f0ec6b82

https://infoscis.github.io/2017/07/21/angular-tutorial-http/

http://han41858.tistory.com/39